The present invention relates to a new and improved method of, and apparatus for, generating by means of a writing laser beam a predetermined pattern on a workpiece containing a three-dimensional integrated circuit and which is provided with a metalized screen. The apparatus of this type is also termed . "laser pattern generator" in the art.
In a method of, and apparatus for, generating a predetermined pattern by means of a writing laser beam as known, for example, from European Patent Publication No. 0,128,993, a scanning laser beam is used in addition to the writing laser beam. During the treatment of the workpiece with the writing laser beam, the scanning laser beam scans the surface of the workpiece. The radiation of the scanning laser beam is reflected by the surface of the workpiece and received and evaluated by means of a radiation detector which may constitute, for example, a differential photodiode. The evaluated measurements are then used for automatically detecting or regulating the movement of the workpiece relative to the writing laser beam.
In a further known method of generating a predetermined pattern by means of a writing laser beam as known, for example, from European Patent Publication No. 0,088,045, there are produced electrically conductive regions in integrated monolithic semiconductor arrangements and there is also described a semiconductor arrangement of high component density which is obtained using this method.
During the manufacture of customized integrated circuits there are used commercially available silicon disks or wafers which are provided with P- and N-structures or N- and P-structures at which specific contact surfaces must be produced which connect these structures and which depend on the purpose of use. Contrary to known technologies there are produced on a silicon disk or wafer electrically conductive regions with standard clearances which are arranged in accordance with a predetermined raster or grid. Such regions and standard clearances can be obtained, for example, by applying an etching or application technique. Depending on the intended circuit configuration, the conductive layer which may be composed, for example, of aluminum and which is present intermediate these clearances, is directly or indirectly removed by means of an electron beam or a beam of electromagnetic radiation. A laser beam is particularly suited for this process and such laser beam can be positioned and controlled in a simple manner and serves to irradiate a photosensitive layer. During such process the silicon disks or wafers are continuously displaced relative to the laser beam along the predetermined raster or grid and the laser power is turned on and turned off by means of a modulator in accordance with the desired removal geometry. The raster or grid spacing is in the order of magnitude of about 1 to about 7 .mu.m, the width of the lines after removal is in the range of about 0.4 to 2 .mu.m, and the treatment rate is in the order of magnitude of 1 to 2 hours per 4" silicon disk or wafer. There thus results a displacement rate in the range of 30 to 100 cm/s and a position tolerance in the range of 0.3 to 2.5 .mu.m at a displacement length of 4". Such values for the position tolerance cannot be obtained using mechanical displacement means or units. The insular conductive regions are thereafter produced by using a photo-etching technique. By using this method expensive photomasks which are specific for each application, can be dispensed with. A semiconductor arrangement obtained in accordance with the aforementioned method comprises in its conductive layer, clearances which are arranged according to the predetermined raster or grid and which clearances constitute the end points or regions and/or the corner points or regions of insular conductive regions.